In current multicast services, when ICP (Internet Content Provider) or multimedia service provider wants to send multimedia service (for example, IPTV operator wants to broadcast a TV channel), it first needs to request the multimedia service management device of the NSP (Network Service Provider) to allocate a multicast network address for the multimedia service for its transmission. Multimedia service guide device (or EPG Server, Electronic Program Guide Server, which is usually provided by ICP) generates multimedia service guides (or program guides) according to the multicast network address allocated by the multimedia service management device and the description of the multimedia service content, etc. When the user equipment wants to receive multimedia service, it first receives multimedia service guides for various kinds of multimedia services provided by ICP from the multimedia service guide device, and for one multimedia service, the multimedia service guides comprise the name of the multimedia service, the description of the multimedia service content, and the multicast network address corresponding to the multimedia service, etc, and the name of the multimedia service, the description of the multimedia service content, etc, are displayed on the screen. The user chooses the multimedia service he/she wants to access according to the name of the multimedia service, the description of the multimedia service content, etc. displayed on the screen, and the user equipment joins the multicast group corresponding to the multicast network address of the multimedia service according to the multimedia service chosen by the user that he/she wants to access, so as to receive the multimedia service which is displayed on the screen.
FIG. 1 illustrates the network topological diagram for the user equipment to receive the multimedia service via the multimedia service guides in the prior art. User equipment is located in the user network, multimedia service management device is located in the NSP network and multimedia service guide device and multimedia service server are located in the ICP network. FIG. 2 illustrates the flowchart of the systematic method for the user equipment to receive multimedia service via multimedia service guides shown in the network topology in FIG. 1. First, in step a1, multimedia service management device notifies the multicast network address allocated for multimedia service to multimedia service guide device via one or more routers, alternatively, it can also notifies the multicast network address allocated for multimedia service to the multimedia service server (the step is not shown in FIG. 2), or notifies the multimedia service server in other manner. The multimedia service guide device generates multimedia service guides according to the received multicast network address of the multimedia service and the description of the multimedia service content, etc. The description of the multimedia service content, etc. can be sent along with the multicast network address by the multimedia service management device, or can be obtained by the multimedia service guide device in other manner, for example, is pre-stored in the multimedia service guide device by ICP.
When the user equipment receives the multimedia service, first, in step b1, the user equipment sends the message to multimedia service guide device for requesting to receive multimedia service guides. Then, in step b2, user equipment receives the multimedia service guides from the multimedia service guide device. Then, in step b5, according to the multimedia service chosen by the user, user equipment joins the multicast group corresponding to the multicast network address of the chosen multimedia service, at last, in step b6, user equipment receives the multimedia service from the multimedia service server.
Since at present, the transmission of the multicast packet is basically based on IPv4 protocol, and the multicast network address resources (i.e., the IP multicast network address) are limited; therefore, when the multicast network address allocated for a certain multimedia service by the multimedia service management device is no longer in use, the multimedia service management device needs to retrieve the multicast network address to reallocate it for other multimedia service to use; therefore, multimedia service management device needs to adjust the allocation of multicast network address frequently. When the multimedia service management device reallocates the multicast network address, the contents of the multimedia service guides in the multimedia service guide device need to be adjusted accordingly, and the multimedia service guide device needs to frequently communicate with the multimedia service management device; For the user equipment, since the multicast network address of the multimedia service changes dynamically, the user equipment needs to frequently communicate with the multimedia service guide device so as to obtain the latest multicast network address of the multimedia service, which waste lots of network bandwidth.